Transmission for a working vehicle and vehicle

ABSTRACT

A transmission for a working vehicle for transmitting drive power from an engine to a driving axle that includes: a flywheel including a flywheel body operatively connected with the engine and a flywheel housing for accommodating the flywheel body; a main-speed-change unit including a main-input shaft operatively connected with the engine via the flywheel body and a main-output shaft for outputting drive power to be transmitted to the driving axle; and a sub-speed-change unit including a sub-input shaft and a sub-output shaft, and disposed at a distance from the main-speed-change unit. The engine, the flywheel and the main-speed-change unit are integrally connected with each other so as to vibrate freely relative to a vehicle frame, and the main-output shaft of the main-speed-change unit is operatively coupled with the sub-input shaft of the sub-speed-change unit via a vibration-absorbing shaft coupling.

CROSS-REFERENCE TO RELATED APPLICATION

The present application is a Continuation of Application Ser. No.11/071,735, filed Mar. 4, 2005, which is a Continuation of ApplicationSer. No. 10/268,676, filed Oct. 11, 2002, now U.S. Pat. No. 6,877,580,the disclosures of which are incorporated in their entireties herein byreference thereto.

FIELD OF THE INVENTION

The present invention relates to a transmission for a working vehiclethat is designed to transmit drive power from an engine to a drivingaxle. The present invention also relates to a vehicle with a powertransmission train designed to transmit drive power from an engine to adriving axle via a main-speed-change unit and a sub-speed-change unit.

BACKGROUND ART

A vehicle such as a working vehicle has a power transmission train,which is designed to transmit drive power from an engine to a drivingaxle via a speed change unit, enabling the driving axle to be rotated ata predetermined speed by the operation of the speed change unit. If aneed exists to widen a speed change range of the driving axle, and/orreduce the load applied to the speed change unit, a sub-speed-changeunit is further provided in addition to a main-speed-change unit.

FIG. 22 is a model view of a conventional vehicle equipped with amain-speed-change unit and a sub-speed-change unit, in which a rear axleserves as a driving axle. As illustrated in this Figure, theconventional vehicle equipped with the sub-speed-change unit has engine801, flywheel 802, main-speed-change unit 803, sub-speed-change unit 804and driving axle unit 805, which are detachable from each other, alignedin sequence from one side of a vehicle to the opposite side thereof inthe longitudinal direction and connected in tandem. This particulararrangement may cause the following problems.

That is, when a hydrostatic transmission (hereinafter referred to asHST) is used as the main-speed-change unit 803, the HST itself vibratesdue to pulsation or the like of operating fluid pressure circulating inthe HST. As mentioned above, the arrangement with the main-speed-changeunit 803, the sub-speed-change unit 804 and the axle unit 805 connectedto each other cause vibrations of the HST to be transmitted to vehicleframe 800 via the sub-speed-change unit 804 and the axle unit 805,thereby causing the problem of deteriorating driving conditions.

In order to solve the above problem, there was proposed an arrangementwherein the engine is connected with the sub-speed-change unit through ahousing, and the HST serving as the main-speed-change unit, is connectedwith the front side of the sub-speed-change unit via an antivibrationmember. The front side of the FIST is then connected with the housingvia another antivibration member.

However, in the above arrangement, there is no consideration made forvibration of the engine. That is, the above power transmissionarrangement causes a problem wherein the housing itself, which supportsthe HST with a flexible structure omitting transmission of vibrations,vibrates due to vibrations transmitted from the engine.

In the above arrangement, the engine, the housing and thesub-speed-change unit are connected in tandem, with the result that aspace does not exist between front and rear wheels. Accordingly, adriver's step must be disposed above those members connected together,which necessitates the driver's step to be disposed at a higher place,and/or those connected members to be disposed at a higher place in acase where a mid-mount mower must be mounted between the front and rearwheels, hence inviting rise of the vehicle's center of gravity.

The present invention has been conceived in consideration of those priorarts. It is an object of the present invention to provide a transmissionfor a working vehicle with a power transmission train designed totransmit drive power from an engine to a driving axle via amain-speed-change unit and a sub-speed-change unit, which is capable ofeffectively preventing vibrations due to the engine and themain-speed-change unit from transmitting to the vehicle frame.

It is another object of the present invention to provide a transmissionfor a working vehicle that is capable of securing a free space betweenthe front and rear wheels without inviting expansion of the vehicle'slength.

It is still another object of the present invention to provide a vehiclewith a power transmission train designed to transmit drive power from anengine to a driving axle via a main-speed-change unit and asub-speed-change unit, which is capable of effectively preventingexpansion of the vehicle's length, as well as securing a free spacebetween the front and rear wheels.

BRIEF SUMMARY OF THE INVENTION

In order to achieve the above objects, there is provided a transmissionfor a working vehicle for transmitting drive power from an engine to adriving axle that includes: a flywheel including a flywheel bodyoperatively connected with the engine and a flywheel housing foraccommodating the flywheel body; a main-speed-change unit including amain-input shaft operatively connected with the engine via the flywheelbody and a main-output shaft for outputting drive power to betransmitted to the driving axle; and a sub-speed-change unit including asub-input shaft and a sub-output shaft, and disposed with a distancefrom the main-speed-change unit. The engine, the flywheel and themain-speed-change unit are integrally connected with each other so as tovibrate freely relative to a vehicle frame, and the main-output shaft ofthe main-speed-change unit is operatively coupled with the sub-inputshaft of the sub-speed-change unit via a vibration-absorbing shaftcoupling.

With the transmission having the above arrangement, vibrations due tothe engine and the main-speed-change unit are effectively prevented fromtransmitting to the vehicle frame, thus contributing to improved runningperformance and running stability of the vehicle. Also, the arrangementwith the main-speed-change unit, which vibrates freely relative to thesub-speed-change unit, being disposed independently at a distance fromthe sub-speed-change unit in the creation of a free space between themain- and sub-speed-change units. This provides an improved designflexibility in designing the working vehicle.

The transmission preferably further includes a damper interposed betweenthe flywheel body and the main-input shaft. With this arrangement,variations in angular speed of the engine are effectively prevented fromaffecting on the main-input shaft of the main-speed-change unit, therebyimproving reliability and durability of the drive train on thedownstream side.

Preferably, the main-input shaft and the main-output shaft of themain-speed-change unit are aligned parallel to each other in thevehicle's vertical direction, that is, one above the other as seen inFIG. 7, and offset to each other in the vehicle's lateral direction.This arrangement can effectively limit the height of themain-speed-change unit, while shortening the width thereof.

The main-speed-change unit preferably includes an output adjustingmember for adjusting the speed change ratio of the main-output shaftwith respect to the main-input shaft, and the output adjusting member isoperated by means of electric signals. This arrangement can achievesimplified coupling mechanism between the output adjusting member andthe operation member disposed in the vicinity of the driver seat.

Preferably, the flywheel housing includes a body portion having anaccommodation space and opposite open ends, and a partition wall fordividing the accommodation space into a first chamber for accommodatingthe flywheel body and a second chamber for accommodating themain-speed-change unit; and the flywheel body has a portion facing thepartition wall, on which an airflow fan is provided.

According to another aspect of the present invention, there is provideda transmission for a working vehicle for transmitting drive power froman engine to a driving axle via a flywheel, an HST and asub-speed-change unit, which are aligned in a power transmissiondirection. The flywheel includes a flywheel body operatively connectedwith the engine and a flywheel housing for accommodating the flywheelbody. The HST includes a hydraulic pump unit having a pump shaft servingas a main-input shaft operatively connected with the engine via theflywheel body, a hydraulic motor unit having a motor shaft serving as amain-output shaft and outputting drive power through the motor shaftwith the speed of the drive power non-stepwisely changed in cooperationwith the hydraulic pump unit, and a center section for supporting thehydraulic pump unit and the hydraulic motor unit and provides fluidconnection therebetween. The engine, the flywheel housing and the HSTare integrally connected with each other so as to vibrate freelyrelative to the vehicle frame and disposed at a distance from thesub-speed-change unit. The sub-speed-change unit includes a sub-inputshaft and a sub-output shaft. The motor shaft of the HST is operativelycoupled with the sub-input shaft of the sub-speed-change unit via avibration-absorbing shaft coupling.

With the transmission having the above arrangement, vibrations due tothe engine and the HST are effectively prevented from transmitting tothe vehicle frame, thus contributing to improved running performance andrunning stability of the vehicle. Also, the arrangement with the HST,which vibrates freely relative to the sub-speed-change unit, beingdisposed independently at a distance from the sub-speed-change unit,results in the creation of a free space between the HST and thesub-speed-change unit. This provides improved design flexibility indesigning the working vehicle.

Preferably, the flywheel housing includes a body portion having anaccommodation space and opposite open ends, and a partition wall fordividing the accommodation space into a dry chamber for accommodatingthe flywheel body and a hydraulic fluid chamber for accommodating theHST, and the flywheel body has a portion facing the partition wall, onwhich an airflow fan is provided.

Preferably, one of the opposite open ends of the flywheel housing, whichis located closer to the hydraulic fluid chamber, is covered by thecenter section.

Preferably, the hydraulic pump unit and the hydraulic motor unit aresupported on an upstream side of the center section; the pump shaft ofthe hydraulic pump unit has a downstream end extending downstreamthrough a downstream side of the center section; and the downstream endof the pump shaft is provided with a charge pump for replenishingoperating fluid in the HST.

Preferably, the downstream end of the pump shaft is further providedwith an auxiliary pump for feeding operating fluid to an outsideactuator.

Preferably, the hydraulic pump unit and the hydraulic motor unit arerespectively supported on upstream and downstream sides of the centersection; and the upstream end of the pump shaft in the hydraulic pumpunit has a portion located in the dry chamber, the portion beingprovided with a charge pump for replenishing operating fluid in the HST.

Preferably, a downstream end of the pump shaft extends downstreamthrough the center section; and a housing for accommodating thesub-speed-change unit is further provided, in which the housing includesa power transmission shaft operatively coupled with the downstream endof the pump shaft via a vibration-absorbing shaft coupling, and anauxiliary pump for feeding operating fluid to an outside actuator, whichis driven by drive power branched from the power transmission shaft.

The flywheel housing preferably includes a PTO shaft, to which drivepower from the engine is selectively transmitted by engagement anddisengagement of clutch means.

The main-output shaft and the PTO shaft are preferably aligned parallelto each other in a vehicle's lateral direction.

According to still another aspect of the present invention, there isprovided a vehicle with a power transmission train for transmittingdrive power from an engine, which is disposed on a vehicle frame closerto a first side thereof in a fore and aft direction of the vehicle, to adriving axle via a main-speed-change unit and a sub-speed-change unit.The main-speed-change unit is integrally disposed with a flywheelhousing that is connected with the downstream side of the engine. Thesub-speed-change unit is disposed on the vehicle frame closer to asecond side thereof in the fore and aft direction of the vehicle at adistance from the flywheel housing. The main-speed-change unit isoperatively coupled with the sub-speed-change unit via a coupling shaftthat extends in the fore and aft direction of the vehicle.

The above arrangement can effectively limit the length of the vehicle,while securing a free space between the front and rear wheels so as toproduce improved design flexibility in designing the vehicle. Forexample, by the utilization of the free space, a driver's step and/or amid-mount mower can be disposed at lower places.

Preferably, the flywheel housing includes a body portion having anaccommodation space and opposite open ends, and a partition wall fordividing the accommodation space into a first chamber and a secondchamber, the former located closer to the first side of the vehicle inthe fore and aft direction, and the latter located closer to the secondside of the vehicle in the fore and aft direction, in which the firstchamber accommodates a flywheel body of the flywheel and the secondchamber accommodates the main-speed-change unit.

The flywheel body preferably has a portion facing the partition wall, onwhich an airflow fan is provided.

Preferably, the engine, the flywheel and the main-speed-change unit aremounted on the vehicle frame so as to vibrate relative to the vehicleframe, and the sub-speed-change unit is mounted on the vehicle frame soas not to vibrate relative to the vehicle frame; and themain-speed-change unit is operatively coupled with the sub-speed-changeunit via a vibration-absorbing shaft coupling. This arrangement caneffectively prevent vibrations due to the engine or the like fromtransmitting to the vehicle frame and the sub-speed-change unit, whilesecurely achieving power transmission between the main-speed-change unitand the sub-speed-change unit.

According to yet another aspect of the present invention, there isprovided a vehicle with a power transmission train for transmittingdrive power from an engine, which is disposed on a vehicle frame closerto a first side thereof in a fore and aft direction of the vehicle, to adriving axle via a flywheel, an HST and a sub-speed-change unit. Theflywheel housing includes a flywheel body operatively connected with theengine and a flywheel housing connected with a side of the engine facinga second side of the vehicle frame in the fore and aft direction of thevehicle so as to accommodate the flywheel body. The HST is integrallydisposed with the flywheel housing. The sub-speed-change unit isdisposed on the vehicle frame closer to the second side in the fore andaft direction of the vehicle at a distance from the flywheel housing.The HST is operatively coupled with the sub-speed-change unit via acoupling shaft that extends in the fore and aft direction of thevehicle.

The above arrangement can effectively limit the length of the vehicle,while securing a free space between the front and rear wheels so as toproduce improved design flexibility in designing the vehicle. Forexample, by the utilization of the free space, a driver's step and/or amid-mount mower can be disposed at lower places.

Preferably, the engine, the flywheel and the HST are mounted on thevehicle frame so as to vibrate relative to the vehicle frame, and thesub-speed-change unit is mounted on the vehicle frame so as not tovibrate relative to the vehicle frame; and the HST is operativelycoupled with the sub-speed-change unit via a vibration-absorbing shaftcoupling. This arrangement can effectively prevent vibrations due to theengine, the HST and the like from transmitting to the vehicle frame andthe sub-speed-change unit, while enabling secured power transmissionbetween the HST and the sub-speed-change unit

Preferably, the flywheel housing is provided with a PTO shaft capable oftransmitting drive power from the engine to the outside of the flywheelhousing via clutch means.

BRIEF DESCRIPTION OF THE DRAWINGS/FIGURES

The above, and other objects, features and advantages of the presentinvention will become apparent from the detailed description thereof inconjunction with the accompanying drawings wherein.

FIG. 1 is a schematic side view of a working vehicle according to afirst embodiment of the present invention.

FIG. 2 is a model view illustrating power transmission of the workingvehicle of FIG. 1.

FIG. 3 is an enlarged side view of an engine and its vicinity in thevehicle of FIG. 1.

FIG. 4 is a schematic front view of the engine of FIG. 3.

FIG. 5 is a front view of a flywheel, an HST and its vicinity in lateralcross section in the working vehicle of FIG. 1.

FIG. 6 is a side view of the flywheel and the HST of FIG. 5 inlongitudinal cross section.

FIG. 7 is a cross section taken along a line VII-VII in FIG. 5.

FIG. 8 is a hydraulic circuit diagram of the working vehicle of FIG. 1.

FIG. 9 is a cross section taken along a line IX-IX in FIG. 5.

FIG. 10 is a cross section taken along a line X-X in FIG. 5.

FIG. 11 is a cross section taken along a line XI-XI in FIG. 5.

FIG. 12 is a cross section taken along a line XII-XII in FIG. 5.

FIG. 13 is a schematic side view of a working vehicle according to asecond embodiment of the present invention.

FIG. 14 is a model view illustrating power transmission of the workingvehicle of FIG. 13.

FIG. 15 is a hydraulic circuit diagram of the working vehicle of FIG.13.

FIG. 16 is a plan view of an HST and its vicinity in lateral crosssection in the working vehicle of FIG. 13.

FIG. 17 is a side view of the HST and its vicinity in longitudinal crosssection in the working vehicle of FIG. 13.

FIG. 18 is an enlarged side view of an engine and its vicinity in theworking vehicle of FIG. 13.

FIG. 19 is a cross section taken along a line IXX-IXX in FIG. 16.

FIG. 20 is a cross section taken along a line XX-XX in FIG. 16.

FIG. 21 is a cross section taken along a line XXI-XXI in FIG. 16.

FIG. 22 is a schematic side view of a conventional working vehicle.

DETAILED DESCRIPTION OF THE INVENTION First Embodiment

The description will be made for a preferred embodiment of the presentinvention with reference to the accompanied drawings. FIGS. 1 and 2 arerespectively a schematic side view of working vehicle 1 of thisembodiment and a model view illustrating power transmission of thevehicle.

As illustrated in FIGS. 1 and 2, the working vehicle 1 includes vehicleframe 10, engine 20 flexibly supported with a vibration absorptionstructure on the vehicle frame 10 closer to a first side thereof withrespect to a fore and aft direction of the vehicle, a main-speed-changeunit and a sub-speed-change unit for respectively performingtransmission of drive power from the engine while changing the speedthereof so that running power is transmitted through thesub-speed-change unit to driving wheels.

FIG. 3 is an enlarged side view of the engine and its vicinity. FIG. 4is a schematic front view of the engine.

As illustrated in FIGS. 3 and 4, attaching bracket 50, which isconnected with the vehicle frame via antivibration rubber 51, issecurely threaded on lateral side walls of the engine 20. That is, theengine can vibrate freely relative to the vehicle frame 10 so thatvibrations from the engine 20 are prevented from transmitting to thevehicle frame 10.

The working vehicle is constructed so that drive power from the engine20 is transmitted to the main-speed-change unit via flywheel 60. Thatis, in the working vehicle, the flywheel 60, the main-speed-change unitand the sub-speed-change unit together constitute a transmission fortransmitting drive power from the engine to a driving axle.

The flywheel 60 and the main-speed-change unit are connected andsupported by the engine 20 and/or the attaching bracket 50 in a freestate (with no direct engagement) with respect to the vehicle frame 10.That is, the engine 20, 91 the flywheel 60 and the main-speed-changeunit are integrally connected with each other, thereby constituting avibratory unit, which can vibrate freely relative to the vehicle frame10.

FIGS. 5 and 6 are respectively a laterally section plan view and alongitudinally section side view of the flywheel 60, main-speed-changeunit 30 and its vicinity.

As illustrated in FIGS. 5 and 6, the flywheel 60 includes flywheelhousing 61 that is connected with the engine 20 and/or the attachingbracket 50 in a free state (i.e., without direct engagement) withrespect to the vehicle frame 10, and flywheel body 65 accommodatedwithin the housing 61 so as to be operatively connected with crankshaft20 a of the engine 20.

The flywheel 60 is preferably provided with damper 66 that is connectedwith an output portion of the flywheel body 65, thereby enabling thepower transmission to the main-speed-change unit of the downstream sidewhile limiting variation in angular speed of the output of the engine,

As illustrated in FIGS. 5 and 6, the flywheel housing 61 has body 62 ofa substantially tubular shape that has opposite open ends (upstream openend and downstream open end) in a power transmission direction, andpartition wall 63 that divides an inner space of the tubular body 62into first chamber 62 a and second chamber 62 b respectively located onthe upstream and downstream sides in the power transmission direction.As used throughout the description, the directional term “upstream” and“downstream” are relative to the power transmission direction.

The first chamber 62 a is designed as a dry chamber for accommodatingthe flywheel body 65 and the damper 66. On the other hand, the secondchamber 62 b is designed as a hydraulic fluid chamber for accommodatingHST 30 serving as the main-speed-change unit and storing operating fluidused for it. The flywheel body 65 has a side facing the partition wall63, which is preferably provided with airflow fan 67, which drawsoutside air into the first chamber 62 a of the flywheel housing 61,thereby cooling the main-speed-change it and hence providing effectivepreventive measure against temperature rise of operating fluid in thehydraulic fluid chamber by means of a simple structure of the fan, whichutilizes rotation of the flywheel body 65. In FIGS. 5 and 6, referencenumeral 68 represents a vent hole formed in a peripheral wall of thetubular body 62.

The HST 30 includes hydraulic pump unit 310 for receiving drive powerfrom the engine 20 via the flywheel 60, hydraulic motor unit 330 fornon-stepwisely changing the speed of drive power from the engine 20 incooperation with the hydraulic pump unit 310, and center section 350that supports the hydraulic pump unit 310 and the hydraulic motor unit330, and forms a hydraulic circuit for fluid connection therebetween. Inthis embodiment, the center section 350 is provided with a pair ofhydraulic lines as the hydraulic circuit, which will be described later.

At least one of the hydraulic pump unit 310 and the hydraulic motor unit330 is of a variable displacement type that has suction/discharge ratesvariable by the operation of an output adjusting member, which cannon-stepwisely change the speed of the output from the hydraulic motorunit 330 by the control of the slanting angle of the output adjustingmember. In this embodiment, the hydraulic pump unit 310 and thehydraulic motor unit 330 are respectively designated as being of thevariable displacement type and a fixed displacement type.

The center section 350 has first side 350 a and second side 350 b, whichrespectively face upstream and downstream in the power transmissiondirection. With both the hydraulic pump unit 310 and the hydraulic motorunit 330 supported on the first side 350 a, the center section 350 isconnected with the tubular body 62 of the flywheel housing 61 so as tocover the downstream open end of the tubular body 62.

That is, in this embodiment, the center section 350 constitutes a partof the flywheel housing 61, and the center section 350, the tubular body62 and the partition wall 63 together define the hydraulic fluid chamber(second chamber) 62 b.

The hydraulic pump unit 310 is, as described above accommodated withinthe hydraulic fluid chamber 62 b of the flywheel housing 61 whilesupported by the center section 350.

More specifically, the hydraulic pump unit 310 includes pump shaft 311that has an upstream end extending into the dry chamber (first chamber)62 a through the partition wall 63 and coupled with the damper 66, and adownstream end extending to the outside through the center section 350,piston unit 312 that performs a rotational movement around the axis ofthe pump shaft 311 by the rotation of the pump shaft 311 and areciprocal movement in association with the rotational movement,cylinder block 313 that supports the piston unit 312, allowing it toperform a reciprocal movement, and is supported on the first side 350 aof the center section 350 so as to be in communication with the pair ofhydraulic lines, output adjusting member 314 that regulates the strokelength of the piston unit 312 according to the slanting angle so as tovary the suction/discharge rates of the piston unit 312, and controlshaft 315 (see the drawings) that adjusts the slanting angle of theoutput adjusting member 314.

In this embodiment, as illustrated in FIGS. 5 and 6, the hydraulic pumpunit 310 is of an axial piston type, which employs a movable swash plateas the output adjusting member 314. In the case where the hydraulic pumpunit is of a radial piston type, a cam ring is employed as the outputadjusting member.

The hydraulic motor unit 330, which is designated as being of the fixeddisplacement type in this embodiment, includes cylinder block 333 thatis supported on the first side 350 a of the center section 350 so as tobe in communication with the pair of hydraulic lines, piston unit 332that is slidably supported within the cylinder block 333 and performs arotational movement as well as a reciprocal movement by means ofpressurized hydraulic fluid from the pair of hydraulic lines, and motorshaft 331 that rotates around the axis by the rotational movement of thepiston unit 332 and has a downstream end extending to the outside(rearwards in this embodiment) through the center section 350. The thusarranged hydraulic motor unit 330 can output rotational output throughthe motor shaft 331 serving as a main output shaft, which output isvariable according to the slanting angle of the output adjusting member314 in the hydraulic pump unit 310.

The vehicle includes charge pump unit 70 driven through the downstreamend of the pump shaft 311, as illustrated in FIGS. 5 and 6. The chargepump unit 70 is used to feed operating fluid to the HST 30, and/or feedoperating fluid to a PTO unit, which will be later described.

Specifically, the charge pump unit 70 includes charge pump casing 71supported on the second side 350 b of the center section 350, and chargepump body 72 that is enclosed by the charge pump casing 71 and driventhrough the downstream end of the pump shaft 311.

The vehicle may be provided with auxiliary pump unit 80 for feedingoperating fluid for driving an outside actuator and/or feeding operatingfluid to a power steering mechanism. By providing the auxiliary pumpunit 80 as well as the charge pump unit 70, it is possible tosufficiently provide operating fluid without applying excessive load tothe charge pump unit 70.

The auxiliary pump unit 80 includes auxiliary pump casing 81 that issupported on a downstream side of the charge pump casing 71, andauxiliary pump body 82 that is enclosed within the auxiliary pump casing81 and driven through the downstream end of the pump shaft 311.

The vehicle of this embodiment further includes PTO unit 90 for drivingan outside unit such as a working unit. In this embodiment, the PTO unit90 is accommodated within the hydraulic fluid chamber 62 b of theflywheel housing 61.

Specifically, the PTO unit 90 includes PTO drive gear 91 that isrelatively non-rotatably supported on the pump shaft 311 so as to bepositioned within the hydraulic fluid chamber 62 b, PTO shaft 92 thathas opposite ends respectively bearing-supported by the partition wall63 and the center section 350, enabling the PTO shaft 92 to be alignedparallel with the pump shaft 311 preferably in the vertical direction(i.e., at a different height from the pump shaft 311 while maintaining aparallel relationship therebetween), PTO driven gear 93 that isrelatively rotatably supported on the PTO shaft 92 so as to be in meshedengagement with the PTO drive gear 91, and hydraulic clutch unit 94 thatperforms engagement/disengagement between the PTO driven gear 93 and thePTO shaft 92.

More specifically, the partition wall 63 of the flywheel housing 61forms opening 63 a through which the PTO unit 90 is insertable, and isalso provided with a detachable lid member 63 b that covers the opening63 a and supports the upstream end of the PTO shaft 92. The thus formedopening 63 a of the partition wall 63 allows the PTO unit 90 to beplaced into the hydraulic fluid chamber 62 b through the dry chamber 62a.

The PTO shaft 92 has a downstream end extending to the outside throughthe center section 350 to have an outer extension through which drivepower for the outside unit can be taken off. The PTO unit 90 ispreferably provided with brake unit 95 between the flywheel housing 61and the PTO shaft 92 so as to apply braking force to the PTO shaft 92 inassociation with a power shutoff action of the hydraulic clutch unit 94with respect to the PTO shaft 92. The thus provided brake unit 95effectively prevents the PTO shaft 92 from rotating due to the moment ofinertia of the outside unit coupled with the PTO shaft, after the powershutoff of PTO shaft 92.

FIG. 7 is a cross section taken along a line VII-VII in FIG. 5. Asillustrated in this Figure, the HST has the pump shaft 311 and the motorshaft 331 aligned parallel to each other in the vehicle's verticaldirection and offset to each other in a vehicle's lateral direction,thereby shortening the length of the HST in the vehicle's lateraldirection while limiting a vertical space to be occupied by theseshafts. Therefore, constitutional members of the vehicle to be disposedabove the HST, such as a driver seat can be disposed as low as possible,thereby contributing to ease of getting-on/off the vehicle and/orcreating a lowered center of gravity of the vehicle. With this shaftarrangement, the pump shaft 311, the motor shaft 331 and the PTO shaft92 are arranged in a triangle as viewed from the front side, so thatthese shafts can be disposed as close as possible to each other withinthe flywheel housing 61. As a result, the size of a combinationcomprising the HST and the PTO unit can be minimized.

In this embodiment, multi-speed mechanical transmission 40 is providedto serve as the sub-speed-change unit.

The multi-speed mechanical transmission 40 is securely supported on thevehicle frame 10 closer to a second end thereof, with a distance fromthe HST 30 serving as the main-speed-change unit in the fore and aftdirection of the vehicle. That is, on the contrary to the vibratoryarrangement that the engine, the flywheel and the HST togetherconstitute a vibratory unit, which can vibrate freely relative to thevehicle frame, the multi-speed mechanical transmission 40 constitutes afixed unit, which is disposed with a distance from the vibratory unit inthe fore and aft direction of the vehicle in such a manner as not tovibrate relative to the vehicle frame.

More specifically, as illustrated in FIGS. 1 and 2, the multi-speedmechanical transmission 40 includes transmission housing 41 and speedchange unit 42 accommodated within the transmission housing 41. Thetransmission housing 41 is connected with housing 111 of axle unit 110having differential gear unit 100 that branches drive power andtransmits the same to a pair of main driving axles 15, and is disposednot to vibrate relative to the vehicle frame.

The speed change unit 42 includes sub-input shaft 43 operatively coupledwith the motor shaft 331, and sub-output shaft 44 disposed so as tostepwisely change the speed between itself and the sub-input shaft 43.With this arrangement, drive power is transmitted from the sub-outputshaft 44 to the differential gear unit 100.

The sub-input shaft 43 is coupled with the motor shaft 331 viavibration-absorbing shaft coupling 120, thereby enabling smoothtransmission of drive power between the motor shaft 331 capable ofvibrating freely relative to the vehicle frame 10 and the sub-inputshaft 43 incapable of vibrating relative to the vehicle frame 10. As thevibration-absorbing shaft coupling 120, a transmission shaft withuniversal joints at its opposite ends can be used.

In this embodiment, as illustrated in FIG. 2, the speed change unit 42includes the sub-input shaft 43, driven shaft 45 disposed substantiallyparallel with the sub-input shaft 43, the sub-output shaft 44 disposedcoaxial with the sub-input shaft 43 so as to be rotatable relative tothe same around the axis, drive gear 46 relatively non-rotatablysupported on the sub-input shaft 43, first driven gear 47 a relativelynon-rotatably supported on the driven shaft 45 in meshed engagement withthe drive gear 46, second and third driven gears 47 b, 47 c disposedwith a distance from the driven gear 47 a in the axial direction in sucha manner as to be relatively non-rotatably supported on the driven shaft45, first output gear 48 a relatively rotatably supported on thesub-output shaft 44 in meshed engagement with the second driven gear 47b, second output gear 48 b relatively rotatably supported on thesub-output shaft 44 in meshed engagement with the third driven gear 47c, first shifter unit 49 a disposed between the sub-input shaft 43 andthe sub-output shaft 44, and second shifter unit 49 b disposed betweenthe second output gear 48 b and the sub-output shaft 44.

The first shifter unit 49 a is designed to be capable of selectivelytaking a low speed position allowing the sub-output shaft 44 to berelatively non-rotatably coupled with the sub-input shaft 43 or thedrive gear 46, a middle speed position allowing the first output gear 48a to be relatively non-rotatably coupled with the sub-output shaft 44,and a neutral position allowing the sub-output shaft 44 to be out ofengagement with the sub-input shaft 43 or the drive gear 46 and with thefirst output gear 48 a.

On the other hand, the second shifter unit 49 b is designed to becapable of selectively taking a high speed position allowing the secondoutput gear 48 b to be relatively non-rotatably coupled with thesub-output shaft 44, and a neutral position allowing them to bedisengaged from each other.

The thus arranged multi-speed mechanical transmission 40 is capable ofproducing drive power adjustable in three stages through the sub-outputshaft 44 by the operation of the first and second shifter units 49 a, 49b.

When employing the PTO unit 90 as in the working vehicle of thisembodiment, the multi-speed mechanical transmission 40 is furtherprovided with power transmission shaft 96 for transmitting drive poweroutputted from the PTO shaft 92 to the outside unit. The PTO shaft 92 isoperatively coupled with vibration-absorbing shaft coupling 120 in thesame as a coupling manner between the motor shaft 331 and the sub-inputshaft 43.

When providing the power transmission shaft 96 in the multi-speedmechanical transmission 40, the driven shaft 45 is preferably formed ina hollow tubular shape to have an inner hollow space, into which thepower transmission shaft 96 is relatively rotatably inserted. Thisarrangement can achieve downsizing of the multi-speed mechanicaltransmission 40 in an embodiment employing a PTO power transmissiontrain.

Reference numerals 97 and 98 in FIG. 2 respectively represent a PTOoutput shaft, and a PTO speed change unit disposed between the powertransmission shaft 96 and the PTO output shaft 97.

As illustrated in FIG. 2, the multi-speed mechanical transmission 40 isfurther provided with a four-wheel-drive unit 410 in this embodiment.The four-wheel-drive unit 410 may be designed to take off drive powerthrough the sub-output shaft 44, allowing itself to easily take offdrive power synchronized with the sub-output shaft 44, which outputsdrive power for the main driving axles 15. The four-wheel-drive unit 410is preferably mounted to the multi-speed mechanical transmission 40 in adetachable manner.

The thus arranged working vehicle produces the following desirableeffects. In the working vehicle of this embodiment, which includes thevibratory unit that can vibrate freely relative to the vehicle frame,and the fixed unit that cannot vibrate relative to the vehicle frame 10,the former being constituted by the integral arrangement of the engine20, the HST 30 serving as the main-speed-change unit and the flywheel60, all of which cause vibrations to the vehicle frame 10, and thelatter being constituted by the multi-speed mechanical transmission 40serving as the sub-speed-change unit, which is disposed with a distancefrom the vibratory unit along the vehicle's longitudinal direction, inwhich the power transmission between the vibratory unit and the fixedunit (i.e., the power transmission between the pump shaft 311 of the HST30 and the sub-input shaft 43 of the multi-speed mechanical transmission40) is performed via the vibration-absorbing shaft coupling 120.

The thus arranged working vehicle can securely perform powertransmission from the HST 30 to the multi-speed mechanical transmission40, while effectively preventing vibrations of the engine and the HSTitself due to pulsation or the like of operating fluid pressure in theHST from transmitting to the fixed unit. As a result, the driveabilityand stability of the vehicle can be remarkably improved.

Moreover, in the working vehicle of this embodiment, the engine 20,which is disposed closer to the first side of the vehicle in the foreand aft direction of the vehicle, has a side facing the second side(opposite to the first side with respect to the fore and aft directionof the vehicle), through which the flywheel housing 61 is connected withthe engine 20. The thus connected flywheel housing 61 accommodates theHST 30 serving as the main-speed-change unit. On the other hand, themulti-speed mechanical transmission 40 serving as the sub-speed-changeunit is connected with the axle unit disposed on the second side of thevehicle in the fore and aft direction of the vehicle with a distancefrom the HST 30, and is also coupled with the HST via their shafts.

That is, the working vehicle with the HST 30 accommodated within theflywheel housing 61 and the multi-speed mechanical transmission 40connected with the axle unit can effectively limit the vehicle's length,while securing a free space between the HST 30 and the multi-speedmechanical transmission 40, thereby providing improved designflexibility in designing a vehicle.

Specifically, the above arrangement produces a design flexibilityenabling such as a driver's step to be disposed above the free space,and/or a mid-mount mower to be disposed below the free space, therebyachieving lowered center of gravity of the vehicle, and improved runningstability of the vehicle.

As described above, in this embodiment, in order to absorb relativevibrations between the HST 30, which serves as a part of the vibratoryunit, and the multi-speed mechanical transmission 40, which serves as apart of the fixed unit, the coupling therebetween is made by thevibration-absorbing shaft coupling 120. Unless relative vibrations occurbetween the HST 30 and the multi-speed mechanical transmission 40, acoupling of a general type may be employed for the couplingtherebetween.

The accommodation of the HST 30 within the flywheel housing 61 producesa desirable effect of lowering costs thanks to decrease in the number ofparts resulted from this arrangement, as well as the above describedeffects.

As another desirable effect, the arrangement with the downstream openend of the flywheel housing 61 covered by the center section 350, whichenables the center section 350 to also serve a part of the flywheelhousing 61, contributes to additional cost reduction.

The description will be hereinafter made for the hydraulic circuit ofthe working vehicle 1.

FIG. 8 illustrates the hydraulic circuit of the vehicle 1. FIGS. 9 and10 are respectively cross sections taken along lines IX-IX and X-X inFIG. 5.

Now, the hydraulic circuit, which uses pressurized hydraulic fluid asoperating fluid fed from the charge pump unit 70.

As illustrated in FIG. 7, the tubular body 62 of the flywheel housing 61forms first suction line 201 with a first end communicated with thehydraulic fluid chamber 62 a and a second end opening to the outside ofthe tubular body 62. The second end of the first suction line 201 iscommunicated with a suction port of suction filter 202 provided in anouter circumference of the tubular body 62. A discharge port of thesuction filter 202 is communicated with the charge pump unit 70 viasecond suction line 203 and conduit 204 (see FIGS. 8 and 10).

As illustrated in FIGS. 2, 5 and 10, the charge pump casing 71 formsthird suction line 205 with a first end opening to the outside so as tobe connected with the conduit 204 and a second end communicated with asuction port of the charge pump body 72, first discharge line 206 with afirst end communicated with a discharge port of the charge pump body 72,flow divider 207 with portion 207 a disposed so as to be communicatedwith a second end of the first discharge line 206, fourth discharge line208 for communication between first output portion 207 b of the flowdivider 207 and a side of the charge pump casing, which faces the centersection 350, PTO discharge line 209 with a first end communicated withsecond output portion 207 c of the flow divider 207 and a second endopening through the side facing the center section 350, PTO on/off valve210 placed in the PTO discharge line 209, and first PTO drain line 211with a first end communicated with a drain portion of the PTO on/offvalve 210 and a second end opening through the side facing the centersection 350.

As illustrated in FIG. 9, the center section 350 forms the pair ofhydraulic lines 220, first bypass line 221 for communication between thepair of hydraulic lines 220, charge line 222 with a first end openingthrough the second side 350 b facing the charge pump casing 71 so as tobe communicated with the fourth discharge line 208 and a second endconnected with the first bypass line 221, charge relief valve 223 placedin the charge line 222, and a pair of high-pressure relief valves 224and a pair of charge check valves 225 placed in the first bypass line221 between a junction point with the charge line 222 and junctionpoints respectively with the pair of hydraulic lines 220.

Preferably, the center section 350 additionally forms second bypass line226 for communication between the pair of hydraulic lines 220, drainline 227 with a first end communicated with the second bypass line 226and a second end communicated with a hydraulic fluid tank, a pair ofsuction valves placed in the second bypass line between a junction pointwith the drain line 227 and junction points respectively with the pairof hydraulic lines 220. The pair of suction valves 228 can effectivelyprevent a negative pressure from being caused in the pair of hydrauliclines 220, thereby preventing the vehicle from being accidentally moveddownwardly on a sloping road (a free wheel phenomenon) when it isstopped with its engine stopped on the sloping road.

The center section 350 also forms a part of a hydraulic passage forcontrolling the hydraulic clutch unit 94 and/or the hydraulic brake unit95 in the PTO unit 90. That is, as illustrated in FIGS. 5 and 9, thecenter section 350 further forms first PTO line 229 with a first endopening through the second side 350 b facing the charge pump casing 71so as to be communicated with the second end of the PTO discharge line209 and a second end opening to the hydraulic fluid chamber 62 b of theflywheel housing 61.

As illustrated in FIG. 5, the second end of the first PTO line 229 iscommunicated with the lid member 63 b of the partition wall 63 in theflywheel housing 61 via hydraulic passage 230 in the form of such as aboring or any other suitable conduit formed in the flywheel housing 61.

FIG. 11 is across section taken along a line XI-XI in FIG. 5. Asillustrated in FIG. 11, the lid member 63 b is provided with second PTOline 231 with a first end communicated with the hydraulic passage 230and a second end opening through a bearing surface of the PTO shaft 92,relief valve 232 placed in the second PTO line 231 for setting theworking pressure of the hydraulic clutch unit 94, and accumulator 233placed in the second PTO line 231 for gradual increase in fluid pressurefed to the hydraulic clutch unit 94.

As illustrated in FIG. 6, the PTO shaft 92 forms hydraulic passage 234communicated with the second PTO line 231, so that pressurized hydraulicfluid fed from the second PTO line 231 via the hydraulic passage 234 isfed to the hydraulic clutch unit 94 and the hydraulic brake unit 95.

The center section 350 further forms a part of a hydraulic passage foran electric-controlled hydraulic servo mechanism as anoutput-adjusting-member control mechanism for controlling the slantingangle of the output adjusting member 314 in the HST 30. That is, theworking vehicle of this embodiment employs electric-controlled hydraulicservo mechanism 500 as the output-adjusting-member control mechanism,which is designed to use a part of pressurized hydraulic fluid from thecharge pump unit 70 as operating fluid.

Now, the description will be made for the electric-controlled hydraulicservo mechanism 500.

The electric-controlled hydraulic servo mechanism 500 is designed to becapable of slantingly moving the output adjusting member 314 by rotatingan outer extension of the control shaft 315 by an effect of hydraulicpressure.

FIG. 12 is a cross section taken along a line XII-XII in FIG. 5.

As illustrated in FIGS. 5 and 12, the electric-controlled hydraulicservo mechanism 500 includes pivoting arm 501 with a first endrelatively non-rotatably connected with the control shaft 315 and asecond end that is a free end crossing the control shaft 315, cylinderblock 502 having a piston accommodation space of a linear shape, cover502 c attached on an outer side wall of the cylinder block 502, piston503 fluid-tightly and axially slidably placed within the pistonaccommodation space so as to divide the piston accommodation space intofirst hydraulic fluid chamber 502 a and second hydraulic fluid chamber502 b, first hydraulic line 504 with a first end communicated with thefirst hydraulic fluid chamber 502 a and a second end formed in a jointsurface between the cylinder block 502 and the cover 502 c so as to opento the outside, second hydraulic line 505 with a first end communicatedwith the second hydraulic fluid chamber 502 b and a second end formed ina joint surface between the cylinder block 502 and the cover 502 c so asto open to the outside, and electromagnetic switching valve (servovalve) 506 disposed on the cover 502 c with first and second outputports 506 a, 506 b formed on an output side respectively communicatedwith the second ends of the first and second hydraulic lines 504, 505and with input port 506C and drain port 506 d formed on an input side.

In association with the operation of the operation member such as ashift lever disposed near the driver seat, the electromagnetic switchingvalve 506 takes a first position enabling communication of the firstoutput port 506 a with the input port 506 c and communication of thesecond output port 506 b with the drain port 506 d, a center holdingposition for shutoff of the respective ports, and a second positionenabling communication of the second output port 506 b with the inputport 506 c and communication of the first output port 506 a with thedrain port 506 d.

In this embodiment, as operating fluid for the hydraulic servomechanism, pressurized hydraulic fluid from the charge pump 70 isutilized.

Specifically, the center section 350 forms servo line 240 with a firstend opening through the second side 350 b of the center section 350facing the charge pump casing 71 so as to be communicated with thefourth discharge line 208 (see FIG. 9). In this embodiment, the secondside 350 b of the center section 350 facing the charge pump casing 71forms groove 240 a for communication between the charge line 222 and theservo line 240, so that a part of pressurized hydraulic fluid comingfrom the fourth discharge line 208 via the groove 240 a flows into theservo line 240.

A second end of the servo line 240 is communicated with the input port506 c of the servo valve 506 via hydraulic passage 241 (see FIG. 7)formed in a peripheral wall of the flywheel housing 61 and hydraulicpassage 242 formed in the cylinder block 502.

The thus arranged hydraulic servo mechanism 500 is actuated in thefollowing manner.

First, the driver operates the operation member to enable a controller(not shown) to excite one solenoid coil of the electromagnetic switchingvalve 506 in association with the operation of the operation member. Theactuated electromagnetic switching valve 506 enables pressurizedhydraulic fluid to be fed into either the first or second hydraulicfluid chamber 502 a, 502 b while being discharged from the residualchamber. Accordingly, the piston 503 is moved towards either side in theaxial direction. Once the piston 503 moves to either side of the axialdirection, the pivoting arm 501 is pivoted so that the control shaft 315is rotated around the axis, thereby slantingly moving the outputadjusting member 314. Upon stoppage of the operation member by thedriver, the controller (not shown) turns off electricity to the solenoidcoil so that the electromagnetic switching valve 506 returns to theholding position. Thus, the slanting movement of the output adjustingmember 314 is halted.

As described above, in this embodiment, the output adjusting member 314of the HST 30 serving as the main-speed-change unit is so arranged as tobe operated by the electric-controlled hydraulic servo mechanism 500.Therefore, this arrangement achieves a simplified structure as comparedwith an arrangement with the operation member connected with the outputadjusting member of the HST via a mechanical operation mechanism such asa linking mechanism or wire mechanism.

That is, as described above, the HST 30 is allowed to vibrate freelyrelative to the vehicle frame 10. Therefore, if the mechanical operationmechanism connects the operation member of such as the driver seat,which is fixed in position so as not to vibrate relative to the vehicleframe 10, with the output adjusting member 314 of the HST 30, vibrationsof the HST 30 relative to the vehicle frame 10 must be absorbed withinthe mechanical operation mechanism. This results in complicatedstructure of the mechanical operation mechanism.

On the contrary, in this embodiment, only the necessary matter is toprovide a wire connection of the electromagnetic switching valve 506with the controller (not shown). As a result, a connection mechanismbetween the operation member and the output adjusting member 314 of theHST 30 can be simplified.

The electric-controlled hydraulic servo mechanism 500 serving as theoutput-adjusting-member control mechanism is preferably provided withneutral-position-return-assist mechanism 550 for biasing the outputadjusting member 314 to the neutral position.

The neutral-position-return-assist mechanism 550 includes torsion spring551 supported around the outer extension of the control shaft 315, andlocking pin 552 which lies at a reference position during the outputadjusting member 314 lies at the neutral position, and upon the slantingmovement of the output adjusting member 314 in directions respectivelyenabling the vehicle to move forward and rearward (i.e., vehicle forwarddirection and vehicle backward direction), pivots around the axis of thecontrol shaft 315 by a displacement amount corresponding to the slantingangle of the output adjusting member 314.

In this embodiment, the locking pin 552 has a proximal end connectedwith the output adjusting member 314 and a distal end extending to theoutside of the flywheel housing 61, while the torsion spring 551 hasfirst and second free ends positioned on the opposite sides of the outerextension in the pivoting direction.

With the above arrangement, the locking pin 552 presses the first andsecond ends of the torsion spring 551, respectively, against the biasingforce of the spring 551 when the output adjusting member 314 pivots inthe vehicle forward and rearward directions.

The neutral-position-return-assist mechanism 550 further includes afixing member for fixing the first and second ends of the torsion spring551 in position, respectively, when the locking pin 552 pivots in thevehicle forward and backward directions. That is, the fixing memberlimits movement of the second end of the torsion spring 551 when thelocking pin 552 presses the first end of the torsion spring 551, andlimits movement of the first end of the torsion spring 551 when thelocking pin 552 presses the second end of the torsion spring 551. Inthis embodiment, fixing pin 553 supported by the cover 502 c serves asthe fixing member.

The fixing pin 553 is preferably an eccentric pin, which has body 553 ainterposed between the opposite ends of the torsion spring 551 andeccentric portion 553 b having an axis eccentric to the body 553 a andextending to the outside through the cover 502 c. With this arrangement,rotation of the eccentric portion 553 b around the axis enables the body553 a to change its position relative to the control shaft 315, andhence the neutral position of the output adjusting member 314 can beeasily adjusted after assembling the HST.

In this embodiment, pressurized hydraulic fluid from the charge pumpunit 70 is thus used not only as fluid replenished to the pair of chargelines 220, but also as operating fluid for driving the output adjustingmember, and operating fluid for driving the hydraulic clutch unit andthe hydraulic brake unit in the PTO unit.

Now, the description will be made for a hydraulic circuit, in whichhydraulic pressurized fluid fed from the auxiliary pump unit 80 is usedas operating fluid.

The auxiliary pump casing 81 forms suction line 251 with a first endopening to the outside and a second end communicated with a suction portof the auxiliary pump body 82, and discharge line 252 with a first endcommunicated with a discharge port of the auxiliary pump body 82 and asecond end opening to the outside (see FIG. 8).

The first end of the suction line 251 is communicated via flexibleconduit 260 such as a rubber tube with auxiliary hydraulic fluid tank280 secured on the vehicle frame 10. The second end of the dischargeline 252 is communicated via flexible conduit 261 such as a rubber tubewith power-steering hydraulic circuit 291 and/or outside-unit-drivinghydraulic circuit 292.

The utilization of the flexible conduits 260, 261 as suction anddischarge conduits of the auxiliary pump unit 80 is due to the reasonmentioned below.

That is, the auxiliary pump unit 80 is supported by the vibratory unitconstituted by the integral connection of the engine 20, the flywheel 60and the HST. The vibratory unit vibrates freely relative to the vehicleframe 10, as described above, and therefore the auxiliary pump unit 80also vibrates freely relative to the vehicle frame 10.

On the other hand, the auxiliary hydraulic fluid tank 280, as well asthe power-steering hydraulic circuit 291 and/or the outside-unit-drivinghydraulic circuit 292 are fixed so as not to vibrate relative to thevehicle frame 1O.

Accordingly, if the suction and discharge conduits of the auxiliary pumpunit 80 are formed from rigid conduits, there may cause twisting of therigid conduits and hence invite leakage of operating fluid. In light ofthis, the flexible conduits 260, 261 are used as the suction conduit anddischarge conduit of the auxiliary pump unit 80.

Oil cooler 265 is placed in conduit 263, through which return fluid fromthe power-steering hydraulic circuit 291 and/or the outside-unit-drivinghydraulic circuit 292 flows. The oil cooler 265 has secondary conduit263 which is a flexible conduit, and passes through the inside of thehydraulic fluid chamber 62 b of the flywheel housing 61 so as to cooloperating fluid stored therein. Operating fluid overflowing from thehydraulic fluid chamber 62 b is finally returned to the auxiliaryhydraulic fluid tank 280 via flexible conduit 264.

Second Embodiment

Now, the description will be made for the second embodiment of thepresent invention with reference to the accompanied drawings. FIGS.13-15 are respectively schematic side view of working vehicle 1′, amodel view of power transmission of the working vehicle, and hydrauliccircuit diagram of the same. In the following description, correspondingor identical parts to those of the first embodiment have been given thesame reference characters or those with primes to omit a detaileddescription thereof.

The working vehicle 1′ of this embodiment is different from the workingvehicle 1 of the first embodiment in the following points:

-   -   (i) The hydraulic pump and the hydraulic motor unit are        respectively supported on the side facing the center section;    -   (ii) The charge pump unit is supported on the partition wall of        the flywheel housing on the upstream side of the hydraulic pump        unit in the power transmission direction;    -   (iii) The downstream end of the pump shaft in the hydraulic pump        unit is used as a PTO shaft;    -   (iv) The auxiliary pump unit is supported on the fixed unit; and    -   (v) The hydraulic clutch unit and the hydraulic brake unit, as        well as the sub-speed-change unit are accommodated within the        transmission housing.

FIGS. 16 and 17 are respectively a plan view in lateral cross sectionand a side view in longitudinal cross section of HST 30′ and itsvicinity.

The HST 30′ includes the hydraulic pump unit 310, the hydraulic motorunit 330, center section 350′ for supporting the hydraulic pump unit 310and the hydraulic motor unit 330.

The center section 350′ has first side 350 a′ facing upstream, whichsupports the hydraulic pump unit 310 thereon, and second side 350 b′facing downstream, which supports the hydraulic motor unit 330 thereon.That is, in this embodiment, the hydraulic pump unit 310 and thehydraulic motor unit 330 are respectively supported on the first andsecond sides 350 a′, 350 b′ of the center section 350′, thereby allowingthe pump shaft 311 and the pump shaft 311 to be positioned as close aspossible to each other, achieving further downsizing of the HST.

The HST 30′ is supported on flywheel housing 61′ in a free state (i.e.,without direct engagement) with respect to the vehicle frame. That is,the HST 30′, as well as the engine 20 and the flywheel 60′ areintegrally connected together so as to constitute a vibratory unit thatvibrates freely relative to the vehicle frame 10.

More specifically, the flywheel 60′ in this embodiment includes theflywheel housing 61′, which has tubular body 62′ similar to the tubularbody 62. The tubular body 62′ is so designed as to be connected with thecenter section 350′ with the hydraulic pump unit 310 and the hydraulicmotor unit 330 supported thereon.

The flywheel housing 6 V is further provided with the cover 64′, whichencloses the hydraulic pump unit 310, the hydraulic motor unit 330, andthe center section 350′, in which the center section 350′ is connectedwith the tubular body 62′ while supporting thereon the hydraulic pumpunit 310 and the hydraulic motor unit 330. That is, in this embodiment,partition wall 63 of the tubular body 62′ and the cover 64′ togetherdefine the hydraulic fluid chamber 62 b. The fly-Wheel housing 61′ ofthis embodiment uses attaching bracket 50′ which has a length extendingbetween the engine 20 and the flywheel housing 61′, since thelongitudinal length of the vehicle is elongated as compared with thefirst embodiment (see FIG. 18).

In this embodiment, charge pump unit 70′ is supported on the partitionwall 63 so as to be positioned within the dry chamber 62 a. Thisarrangement allows the pump shaft 311 and the motor shaft 331 to bepositioned as close as possible to each other. That is, in thisembodiment, the hydraulic pump unit 310 and the hydraulic motor unit 330are respectively supported on the first and second sides 350 a′, 350 b′of the center section 350′ so as to achieve minimized the shaft distancebetween the pump shaft 311 and the motor shaft 331. In the case of thisarrangement, if the charge pump unit 70′ is supported on the second side350 b′ of the center section 350 or the cover 64′, the pump shaft 311and the motor shaft 331 must be spaced apart from each other so as toprevent intervention between the charge pump unit 70′ and the motorshaft 331.

On the contrary, in this embodiment, the charge pump unit 70′ issupported on the partition wall 63 on the upstream side of the hydraulicpump unit 310, so that no consideration to prevent intervention betweenthe charge pump unit 70′ and the hydraulic motor unit 330 may be needed.Therefore, it is possible to achieve minimized distance between the pumpshaft 311 and the motor shaft 331.

In this embodiment, the downstream end of the pump shaft 311 is used asthe PTO shaft, thereby achieving simplified structure of the PTO unit90.

That is, in this embodiment, as described above, the charge pump unit70′ is not disposed on the downstream end of the pump shaft 311, but onthe upstream side of the hydraulic pump unit 310. Accordingly, the thingto do for using the pump shaft 311 as the PTO shaft is only to have thedownstream end of the pump shaft 311 extending downstream through thecenter section 350′ and the cover 64′.

As illustrated in FIG. 14, the downstream end of the pump shaft 311 isoperatively coupled with the power transmission shaft 96 via thevibration-absorbing shaft coupling 12O. In this embodiment, PTO clutchunit 94′ and PTO brake unit 95′ are provided in the fixed unit.Specifically, the PTO clutch unit 94′ and the PTO brake unit 95′ aredisposed on the power transmission shaft 96 within transmission housing41′.

In this embodiment, the auxiliary pump unit 80′ is disposed on thedownstream side of the vibration-absorbing shaft coupling 120. That is,the auxiliary pump unit 80′ is supported by the fixed unit disposed witha distance from the vibratory unit constituted by the engine 20, theflywheel 60′ and the HST 30′ so as not to vibrate relative to thevehicle frame.

Specifically, the auxiliary pump unit 80′ Includes auxiliary pump casing81′ secured to the transmission housing 41′, auxiliary pump body 82′enclosed by the auxiliary pump casing 81′, and a power transmissionmechanism for providing constant connection between the auxiliary pumpbody 82′ and the power transmission shaft 96 located on the upstreamside of the PTO clutch unit 94′.

Now, the description will be made for the hydraulic circuit of theworking vehicle of this embodiment with reference to FIG. 15.

Pressurized hydraulic fluid from the charge pump unit 70′ Is fed to thecharge line 222 as charging fluid, as well as fed to the servo line 240.

FIGS. 19-21 are respectively cross sections taken along lines IXX-IY-Xto XXI-XXI in FIG. 16.

As illustrated in FIG. 19, the tubular body 62′ is connected with thesuction filter 202, and forms the first suction line 201 forcommunication between the hydraulic fluid chamber 62 b and the suctionport of the suction filter 202, and the second suction line 203 forcommunication between the discharge port of the suction filter 202 andthe charge pump.

As illustrated in FIG. 20, the charge pump casing 71′ of the charge pump70′ forms the third suction line 205 for communication between thesecond suction line 203 and the suction port of the charge pump body72′, and the first discharge line 206 with the first end communicatedwith the discharge port of the charge pump body 72′.

As illustrated in FIG. 16, the tubular body 62′ further forms the fourthdischarge line 208 for communication between the first discharge line206 and the charge line 222 in the center section 350′, and hydraulicpassage 242 branched from the fourth discharge line 208 and communicatedwith the input port 506 c of the servo valve 506.

As illustrated in FIG. 21, the center section 350′ forms a hydraulicpassage in the same manner as the center section 350 of the firstembodiment.

Thus, in this embodiment, pressurized hydraulic fluid from the chargepump unit 70′ is used as replenishing fluid to the pair of charge tines220 and operating fluid driving the servo valve 506.

On the other hand, as illustrated in FIG. 15, pressurized hydraulicfluid from the auxiliary pump unit 80′ is used as operating fluid forthe hydraulic clutch of the multi-speed mechanical transmission, as wellas operating fluid for the hydraulic clutch unit 94 and/or the hydraulicbrake unit 95 in the PTO unit, operating fluid for the power steeringand operating fluid for driving the outside unit.

That is, as illustrated in FIGS. 15 and 16, in this embodiment,multi-speed mechanical transmission 40′ serving as the sub-speed-changeunit includes hydraulic clutch units 49 a′-49 c′ to change the speed byutilizing a part of pressurized hydraulic fluid from the auxiliary pump80′.

In this embodiment, it is possible to achieve cost reduction of conduitmembers in the auxiliary pump unit, as well as producing the samedesirable effects as the first embodiment.

That is, the auxiliary pump unit 80′ of this embodiment is supported bythe fixed unit disposed with a distance from the vibratory unitconstituted by the engine 20, the flywheel 60′ and the HST 30′, andoperatively coupled with the pump shaft 311 of the fixed unit via thevibration-absorbing shaft coupling 120. This arrangement omits thenecessity to form suction conduit 260′ and discharge conduit 261′ in theauxiliary pump unit 80′ by flexible conduits, enabling further costreduction of the conduit members as compared with the first embodiment.Also, durability of the conduits can be improved thanks tonon-transmission of vibrations from the engine and/or the HST to thesuction conduits, discharge conduits or the like.

This specification is by no means intended to restrict the presentinvention to the preferred embodiments set forth therein. Variousmodifications to the transmission for the working vehicle, and thevehicle as described herein, may be made by those skilled in the artwithout departing from the spirit and scope of the present invention asdefined in the appended claims.

1. A housing for accommodating a hydraulic pump and a hydraulic motorthat form an HST and supporting a pump shaft and a motor shaft thatrespectively support the hydraulic pump and the hydraulic motor,comprising: a body having an upstream side and a downstream side in apower transmission direction, the upstream side being connected directlyor via an attaching bracket to an engine having an output shaft to whicha flywheel body is connected, the downstream side being configured sothat a center section forming a pair of hydraulic lines for fluidlycommunicating between the hydraulic pump and the hydraulic motor isconnected thereto; and a partition wall dividing the body into a drychamber which is on an upstream side in the power transmission directionand in which the flywheel body is positioned and a hydraulic fluidchamber which is on a downstream side in the power transmissiondirection and in which the hydraulic pump and the hydraulic motor arepositioned, the hydraulic fluid chamber being capable of storingoperating fluid for the HST in cooperation with the center section,wherein the partition wall supports the pump shaft, the motor shaft anda PTO shaft in cooperation with the center section, and the hydraulicfluid chamber accommodates, in addition to the hydraulic pump and thehydraulic motor, a transmission gear for operatively connecting the pumpshaft and the PTO shaft, and a PTO hydraulic clutch unit supported bythe PTO shaft so as to perform engagement or disengagement of the powertransmission from the pump shaft to the PTO shaft.
 2. A housingaccording to claim 1, wherein: the partition wall forms an openingthrough which the PTO hydraulic clutch unit is insertable, and theopening is covered with a lid member.
 3. An HST that is integrallyconnected to an engine having an output shaft to which a flywheel bodyis connected, comprising: a hydraulic pump; a hydraulic motor fluidlycommunicated with the hydraulic pump; a housing for accommodating thehydraulic pump and the hydraulic motor; a pump shaft supported by thehousing in a state where the pump shaft supports the hydraulic pump in arelatively non-rotatable manner and is connected to the output shaftthrough the flywheel body; a motor shaft supported by the housing in astate where the motor shaft supports the hydraulic motor in a relativelynon-rotatable manner; a PTO shaft operatively connected to the pumpshaft; a PTO hydraulic clutch unit supported by the PTO shaft so as toperform engagement or disengagement of the power transmission from thepump shaft to the PTO shaft; and an auxiliary pump unit driven by thepump shaft, the auxiliary pump unit being used to feed operating fluidto the PTO hydraulic clutch unit; wherein the housing includes, a bodyhaving an upstream side and a downstream side in a power transmissiondirection, the upstream side being connected directly or via anattaching bracket to an engine so as to allow the pump shaft to beconnected to the output shaft through the flywheel body, the downstreamside having an opening through which the hydraulic pump and thehydraulic motor pass; a partition wall dividing the body into anupstream side in the power transmission direction where the flywheelbody is positioned and a downstream side in the power transmissiondirection where the hydraulic pump, the hydraulic motor and the PTOhydraulic clutch unit are positioned; and a center section connected tothe body so as to cover the opening.
 4. An HST according to claim 3,wherein: the partition wall forms an opening through which the PTOhydraulic clutch unit is insertable, and the opening is covered with alid member.
 5. A working vehicle configured so that running power istransmitted from an engine, which is supported by a vehicle frame, todriving wheels through an HST, wherein: the HST is connected to theengine in a free state with respect to the vehicle frame; the HST isprovided with an electric-controlled hydraulic servo mechanism forslantingly moving an output adjusting member in the HST and an auxiliarypump unit that is driven by the pump shaft and that functions as ahydraulic source for the electric-controlled hydraulic servo mechanism,the auxiliary pump unit being connected to an assembly formed by theengine and HST so as to integrally vibrate along with the assembly withrespect to the vehicle frame; and the electric-controlled hydraulicservo mechanism includes an electromagnetic switching valve that changesa flowing direction of a hydraulic fluid from the auxiliary pump unit inassociation with an operation member disposed near a driver seat in theworking vehicle.